When utilizing various types of pneumatic cylinders, two types of cylinders exist. One type is where the cylinder provides force only at the end of its travel. The remaining type of cylinders requires force throughout their stroke. In both cases, the position is determined by loading against a hard stop in the cylinder, an external hard stop or an immovable object in the path of motion.
Electrical linear drives or electric drive cylinders exist in the industry. These linear drives are utilized for force output applications. Most of the drives are designed for positioning and not for force generation. The drives are very complex and costly. They contain controllers that utilize programming that provides deceleration of the piston prior to contacting the end stops.
A problem exists in that the linear drives are not utilized for general applications. This is especially the case where a hard stop is contacted. Here, the entire device receives a shock load that usually damages the entire drive train unless deceleration is preprogrammed into the linear drive. In many of these applications, the positioning point of where the device meets the load, may not be known. Thus, this point cannot be programmed into the controller in advance of contacting the object. Also, these devices increase the costs of the device which, in turn, makes them an unattractive solution for simple force generation applications. Additionally, where electric linear drives are utilized in air cylinder applications, the electrical linear drive is usually much larger than its pneumatic counterpart. Accordingly, to be acceptable, the device must have a size relative to that of the pneumatic cylinder.